Barrel unit and image pickup apparatus

ABSTRACT

A barrel unit includes a barrel, a holding member configured to hold an optical element, a cylindrical member configured to support the barrel and the holding member, and a driving unit configured to generate a thrust by electrifying in a magnetic field formed by a magnet and a yoke a coil fixed onto the cylindrical member and to drive the holding member in an optical axis direction of the optical element by using the thrust. The yoke, the magnet, and the coil are located outside of a part of the cylindrical member which supports the barrel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a barrel unit and an image pickupapparatus.

2. Description of the Related Art

Japanese Patent Laid-Open No. (“JP”) 2004-336857 discloses a drivingunit used for a lens barrel unit. This driving unit includes a lensholding frame configured to move in an optical axis direction, a drivingcoil fixed onto the lens holding frame and having a winding directionperpendicular to the optical axis direction, a plate-shaped drivingmagnet parallel to the optical axis direction, and a yoke that extendsparallel to the optical axis direction and is configured to fix thedriving magnet. The lens holding frame is moved in the optical axisdirection by a primary guide shaft and a secondary guide shaft.

However, the driving unit disclosed in JP 2004-336857 has a room ofminiaturization.

SUMMARY OF THE INVENTION

A barrel unit according to one aspect of the present invention includesa barrel, a holding member configured to hold an optical element, acylindrical member configured to support the barrel and the holdingmember, and a driving unit configured to generate a thrust byelectrifying in a magnetic field formed by a magnet and a yoke a coilfixed onto the cylindrical member and to drive the holding member in anoptical axis direction of the optical element by using the thrust. Theyoke, the magnet, and the coil are located outside of a part of thecylindrical member which supports the barrel.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a barrel unit according to afirst embodiment of the present invention.

FIG. 2 is an exploded perspective view of a zoom deceleration unitillustrated in FIG. 1.

FIG. 3 is an exploded perspective view of a focus driving mechanismillustrated in FIG. 1.

FIG. 4 is a front view illustrating that the focus driving mechanismillustrated in FIG. 3 is incorporated into a fixture base plate.

FIG. 5 is a front view illustrating that the focus driving mechanism andthe fixture base plate illustrated in FIG. 3 are incorporated into afixture cylinder illustrated in FIG. 1.

FIG. 6 is a side view of the lens holding frame illustrated in FIG. 3.

FIG. 7 is a perspective view of the lens holding frame illustrated inFIG. 3.

FIG. 8 is a perspective view of a yoke incorporated with a magnetillustrated in FIG. 3.

FIGS. 9A to 9E are sectional views illustrating a movement of a coil fora magnet illustrated in FIG. 8.

FIG. 10 is a partially sectional view of a barrel unit illustrated inFIG. 1.

FIG. 11 is a partially sectional view of a barrel unit illustrated inFIG. 1.

FIG. 12 is a partially sectional view of the barrel unit illustrated inFIG. 1.

FIGS. 13A and 13B are sectional views illustrating a movement of a coilfor a magnet according to a second embodiment.

DESCRIPTION OF THE EMBODIMENTS

Referring now to the accompanying drawings, a description will be givenof embodiments of the present invention.

First Embodiment

FIG. 1 is an exploded perspective view of a barrel unit that can bemounted on a camera (image pickup apparatus). The barrel unit includes afirst barrel 1, a second barrel 3, a linear movement cylinder 5, arotation cylinder 6, a fixture cylinder (cylindrical member) 7, a zoomdeceleration mechanism 8, a fixture base plate 10, a focus drivingmechanism 11, and a CCD image sensor 12.

The first barrel 1 holds a first lens unit (not illustrated) and abarrier 2, and three cam followers 1 a are attached to an outercircumferential surface of the first barrel 1 in the circumferentialdirection. These three cam followers 1 a perforate three linear movementgrooves 5 a that are formed in the linear movement cylinder 5 and extendin the optical axis direction OA. The three cam followers 1 a areengaged with three cam grooves 6 a formed in the inner circumferentialsurface of the rotation cylinder 6.

The second barrel 3 holds a second lens unit L2 and a shutter (notillustrated), and three cam followers 3 a are attached to an outercircumferential surface of the second barrel 3 in the circumferentialdirection. The three cam followers 3 a perforate three linear movementgrooves 5 b of the linear movement cylinder 5 and are engaged with thethree cam grooves 6 b of the rotation cylinder 6.

The linear movement cylinder 5 restricts rotations of the first barrel 1and the second barrel 3, and is supported by the inner circumference ofthe rotation cylinder 6. Three projections 5 d are formed on the outercircumferential surface of a flange portion 5 c of the linear movementcylinder 5 in the circumferential direction. The three projections 5 dare engaged with three linear movement grooves 7 a that are formed in aninner circumferential surface of the fixture cylinder 7 and extend inthe optical axis direction OA.

The rotation cylinder 6 moves both the first barrel 1 and the secondbarrel 3 in the optical axis direction OA. Three cam followers 6 c and agear 6 d are formed on the outer circumferential surface of the rotationcylinder 6 in the circumferential direction. The three cam followers 6 care engaged with three cam grooves 7 b formed on an innercircumferential surface of the fixture cylinder 7, and the gear 6 d isengaged with a deceleration gear 21 of the zoom deceleration mechanism8.

The fixture cylinder 7 movably supports the first barrel 1, the secondbarrel 3, and the rotation cylinder 6 in the optical axis direction OA,and holds the zoom deceleration mechanism 8. The fixture cylinder 7 isfixed onto the fixture base plate 10 via five screws 9.

The fixture base plate 10 supports the fixture cylinder 7, the zoomdeceleration mechanism 8, the focus driving mechanism 11, and the CCDimage sensor 12. The fixture base plate 10 includes a rotationrestricting shaft 10 a and a substrate portion 10 b.

The substrate portion 10 b has a flat plate shape perpendicular to theoptical axis direction OA, and the rotation restriction shaft 10 aextends perpendicular to the substrate portion 10 b (or parallel to theoptical axis direction OA) and is fixed onto the substrate portion 10 b.The substrate portion 10 b includes a hollow cylinder portion 10 c thatextends parallel to the optical axis direction OA. The substrate portion10 b further includes a yoke fixture portion 10 d used to fix a yoke 28and arranged outside of the fixture cylinder 7 in the assembly time.

The yoke fixture portion 10 d stands parallel to the optical axisdirection OA from the substrate portion 10 b, and has a U-shaped sectionand a semicircular projection 10 d ₁ on its top surface. The projection10 d ₁ has a perforation hole 10 d ₂ formed parallel to the optical axisdirection.

FIG. 2 is an exploded perspective view of the zoom decelerationmechanism 8. Reference numeral 13 denotes a motor, and a decelerationgear 14 is press-fitted with the tip of the motor 13. The motor 13 isfixed onto the fixture base plate 10 via two screws 15. A decelerationgear 16 to a deceleration gear 21 are rotatably supported on the fixturebase plate 10, and held by the fixture cylinder 7. The deceleration gear21 is engaged with the gear 6 d of the rotation cylinder 6.

When a main switch (not illustrated) is turned on, the motor 13 rotatesand the driving force of the motor 13 is transmitted to the gear 6 d ofthe rotation cylinder 6 from the deceleration gear 14 to thedeceleration gears 16, 17, 18, 19, 20, and 21 in this order. Therotation cylinder 6 to which the driving force is transmitted rotatesand moves in the optical axis direction OA while the cam followers 6 crotates along the cam grooves 7 b of the fixture cylinder 7. At thistime, the linear movement cylinder 5 supported on the innercircumference of the rotation cylinder 6 moves in the optical axisdirection OA without rotating because the linear movement cylinder 5 isrestricted from rotating due to the engagements between the projections5 d of the linear movement cylinder 5 and the linear movement grooves 7a of the fixture cylinder 7.

When the rotation cylinder 6 rotates, the first barrel 1 moves in theoptical axis direction OA along the cam grooves 6 a of the rotationcylinder 6. At this time, the first barrel 1 moves in the optical axisdirection OA without rotating because the first barrel 1 is restrictedfrom rotating due to the engagements between the cam followers 1 a andthe linear movement grooves 5 a of the linear movement cylinder 5. Inaddition, the second barrel 3 is moved in the optical axis direction OAalong the cam grooves 6 b of the rotation cylinder 6. At this time, thesecond barrel 3 moves in the optical axis direction OA without rotatingbecause the second barrel 3 is restricted from rotating due to theengagements between the cam followers 3 a of the second barrel 3 and thelinear movement grooves 5 b of the linear movement cylinder 5.

The focus driving mechanism 11 serves as a driving unit configured todrive in the optical axis direction OA a lens holding frame 22configured to hold a third lens unit L3 as an optical element as anobject to be driven. This driving unit can broadly apply a driving unitthat is configured to generate a thrust in a coil and to drive a holdingmember configured to hold the coil and the member to be driven throughthe thrust by electrifying the coil that is arranged between a yoke anda magnet.

FIG. 3 is an exploded perspective view of the focus driving mechanism11. FIG. 4 is a front (or plane) view illustrating that the focusdriving mechanism 11 is incorporated into the fixture base plate 10.FIG. 5 is a perspective view illustrating that the focus drivingmechanism 11 and the fixture base plate 10 are incorporated into thefixture cylinder 7.

FIG. 6 is a side view illustrating a relationship between a sleeveportion 22 a and a fixture portion 22 d of the lens holding frame 22.FIG. 7 is a perspective view of the lens holding frame 22 into which thecoil 24 is incorporated. FIG. 8 is a perspective view of the yoke 28into which the magnet 29 is incorporated.

The lens holding frame 22 includes a sleeve portion 22 a, an arm portion22 c, and a body 22 f. The lens holding frame 22 is a holding memberconfigured to move parallel to the optical axis direction OA. The body22 f holds the third lens unit L3 as an object to be driven.

The body 22 f has a rotation restricting portion 22 b that forms aperforation hole at the outer circumferential edge. The rotationrestriction portion 22 b is perforated by the rotation restricting shaft10 a arranged in a cylindrical portion 7 d (illustrated by a brokenline) of the fixture cylinder (cylindrical member) 7, as illustrated inFIG. 4. Since the rotation restricting shaft 10 a is fixed onto thesubstrate portion 10 b, the body 22 f can be guided by the rotationrestricting shaft 10 a without rotating and can be moved parallel to theoptical axis direction OA.

The plate-shaped arm portion 22 c is fixed onto an outer circumferentialposition of the body 22 f opposite to the rotation restricting portion22 b with respect to the center of the third lens unit L3, and extendsin a (radial) direction orthogonal to the optical axis direction OA. Thearm portion 22 c passes a notch portion 7 c formed in a space betweenthe linear movement groove 7 a and the cam groove 7 b of the fixturecylinder 7, as illustrated in FIGS. 1 and 5. In addition, the armportion 22 c has such a length that the guide shaft 23 and the coil 24can be located outside of the fixture cylinder 7. Thereby, the barrelunit can be made small.

The sleeve portion 22 a stands parallel to the optical axis direction OAfrom the arm portion 22 c, and is located outside of the cylindricalportion 7 d (illustrated by the broken line) of the fixture cylinder 7,as illustrated by FIG. 4. The sleeve portion 22 a includes anapproximately rectangular parallelepiped body 22 a ₁, and a bottom of aninner side surface 22 a ₃ of the body 22 a ₁ is connected to the armportion 22 c.

The sleeve portion 22 a includes a perforation hole 22 a ₂ thatperforates top and bottom surfaces of the body 22 a ₁, an approximatelyrectangular parallelepiped fixture portion 22 d that projects to theoutside from an outer side surface opposite to the inner side surface 22a ₃, and a holder 22 e formed on a side surface that is perpendicular tothe top and bottom surfaces, the inner side surface, and the outer sidesurface of the body 22 a ₁.

A guide shaft 23 is inserted into the perforation hole 22 a ₂. One endof the guide shaft 23 contacts a bottom surface of a projection 7 e ofthe fixture cylinder 7 and fixed onto the projection 7 e via a screw(not illustrated) and screw holes 7 e ₁. The other end of the guideshaft 23 is inserted into a hollow portion of the hollow cylinderportion 10 c of the fixture base plate 10. After the guide shaft 23 isinserted into the perforation hole 22 a ₂ via a spring 30, the guideshaft 23 contacts the bottom surface of the projection 7 e via aperforation hole 25 a of a flexible substrate 25. In addition, the guideshaft 23 is arranged in an opening 28 b of the yoke 28, as illustratedin FIG. 4.

The guide shaft 23 is supported parallel to the optical axis directionOA between the fixture cylinder 7 and the fixture base plate 10, andthus the sleeve portion 22 a can be moved parallel to the optical axisdirection OA while guided by the guide shaft 23.

The fixture portion 22 d is arranged in a bilateral symmetry withrespect to the body 22 a ₁ of the sleeve portion 22 a, as illustrated inFIG. 6. The fixture portion 22 d is inserted into an air core portion 24a of the coil 24 at a position opposite to the rotation restrictingportion 22 b with respect to the center of the third lens unit L3, asillustrated in FIG. 7. As illustrated in FIG. 4, the fixture portion 22d is arranged in a housing space 28 e of the yoke 28.

The holder 22 e fixes the encoder magnet 26.

The coil 24 includes a first driving force generator 24 b and a seconddriving force generator 24 c each configured to generate a drivingforce. The coil 24 is held and fixed by the sleeve portion 22 a of thelens holding frame 22 as a result of that the fixture portion 22 d ofthe lens holding frame 22 is inserted into the air core portion 24 athat extends in the (center axis) direction (F) orthogonal to theoptical axis direction OA, as illustrated in FIG. 7. Therefore, the coil24 moves parallel to the optical axis direction OA together with thelens holding frame 22 while the coil 24 is fixed onto the lens holdingframe 22.

The coil 24 is wound around its center axis direction F. Morespecifically, the coil 24 includes a pair of winding portions parallelto the optical axis direction OA, and a pair of winding portion parallelto a (driving current flowing) direction D perpendicular to both thecenter axis direction F and the optical axis direction OA. Asillustrated in FIG. 7, the first driving force generator 24 b and thesecond driving force generator 24 c of the coil 24 are winding portionsparallel to the direction D, and the first driving force generator 24 bis located under the second driving force generator 24 c (or on theimage pickup surface side).

In this embodiment, the driving unit includes the guide shaft 23 engagedwith the lens holding frame 22 and configured to guide a movement of thelens holding frame 22. The lens holding frame 22 includes the sleeveportion 22 a, and the sleeve portion 22 a includes the perforation hole22 a ₂ (engagement portion) engaged with the guide shaft 23, and thefixture portion 22 d inserted into the air core portion 24 a of the coil24 and configured to fix the coil 24.

Since JP 2004-336857 arranges a guide member of a primary guide shaftand a driving coil distant from each other, an operational failure ofthe lens holding frame may occur due to pinching of the guide member asthe guide member, into which the primary guide shaft is inserted,becomes shorter in the optical axis direction.

On the other hand, since this embodiment holds the guide shaft 23 andthe coil 24 on the sleeve portion 22 a, the coil 24 is close to theguide shaft 23. As a result, even when an engagement length (which is alength of the perforation hole 22 a ₂) parallel to the optical axisdirection OA between the guide shaft 23 and the sleeve portion 22 abecomes shorter, the operational failure of the lens holding frame 22 isless likely to occur.

This effect is enhanced by symmetrically arranging the coil 24 withrespect to the plane that passes the center axis of the guide axis 23and the center axis of the air coil portion 24 a of the coil 24. This isbecause no force is applied to the guide shaft 23 in a direction thatinclines to the center axis of the guide shaft 23, when the coil 24moves. This plane is a plane that passes a line M and is perpendicularto the paper plane of FIG. 4, or a plane perpendicular to the paperplane of FIG. 6 and passes an alternate long and short dash line.

In addition, the top and bottom surfaces of the body 22 a ₁ having theperforation hole 22 a ₂ are adjacent and orthogonal to the outer sidesurface on which the fixture portion 22 d is provided. Since JP2004-336857 arranges the center axis of the air core portion of the coilparallel to the optical axis direction, the driving unit becomes largedue to the space of the coil. On the other hand, this embodimentminiaturizes the barrel unit by arranging the center axis of the aircore portion of the coil 24 perpendicular to the optical axis direction.

In addition, according to this embodiment, the sleeve portion 22 a isengaged with the guide shaft 23 and holds the coil 24, and the centeraxis of the rotation restricting shaft 10 a, the optical axis, and thecenter axis of the guide shaft 23 are approximately arranged on the sameline M. The coil 24 includes the winding portions (driving forcegenerators 24 b and 24 c) in which the current flows in the directionperpendicular to both the optical axis direction OA and the center axisdirection F. Moreover, an axis K illustrated in FIG. 7 corresponds to analternate long and short dash line in FIG. 6, is parallel to the opticalaxis direction OA, and halves a length of these winding portions in thedirection D. The axis K is located on the plane that is perpendicular tothe paper plane of FIG. 4 and passes the line M or the plane that isperpendicular to the paper plane of FIG. 6 and passes the alternate longand short dash line. Therefore, this embodiment can reduce drivingnoises, because the engagement states the guide shaft 23 and therotation restricting shaft 10 a little change, even when the coil 24 iselectrified and moved by an attraction force to the magnet 29.

On the other hand, according to JP 2004-336857, the coil is a separatemember from the guide member into which the primary guide shaft isinserted, and the coil is arranged at a position that shifts from a linethat passes the center axes of the primary guide shaft and the secondaryguide shaft (see FIG. 3 of JP 2004-336857). Therefore, according to FIG.3 of JP 2004-336857, as the coil longitudinally displaces, for example,an engagement state varies between the secondary guide shaft and anengagement notch into which the secondary guide shaft is inserted andthe driving noises occur due to the loose engagement.

The coil 24 is arranged apart from the magnet 29 by a predetermineddistance in the housing space 28 e of the yoke 28, as illustrated inFIG. 4.

The flexible substrate 25 is fixed onto the lens holding frame 22, andelectrically connected to the coil 24 as illustrated in FIG. 7.

The encoder magnet 26 extends parallel to the optical axis direction OA,is fixed into the holder 22 e of the lens holding frame 22, and movesparallel to the optical axis direction OA together with the lens holdingframe 22. An MR sensor 27 as a magnetic sensor is fixed onto the fixturebase plate 10, and arranged opposite to the encoder magnet 26.

When the encoder magnet 26 moves together with the lens holding frame 22relative to the MR sensor 27, the magnetism affecting the MR sensor 27varies and the output from the MR sensor 27 changes. Based on thisoutput change, a CPU (not illustrated) can detect a position of the lensholding frame 22 in the optical axis direction OA. The CPU controls acurrent that is supplied to the coil 24 via the flexible substrate 25 byreferring to positional information of the lens holding frame 22detected through the MR sensor 27, and thereby the CPU moves the thirdlens unit L3 to a target position.

The yoke 28 has a rectangular pole shape that extends parallel to theoptical axis direction OA, is housed in a yoke fixture portion 10 d ofthe fixture base plate 10, is fixed onto the yoke fixture portion 10 dby fastening the screw 9 into the perforation hole 10 d ₂ of theprojection 10 d ₁ and a perforation hole 28 h ₁ of a projection 28 h.

The yoke 28 includes a fixture yoke 28 a onto which the magnets 29 arefixed, a pair of opposite yokes 28 c arranged parallel and opposite tothe fixture yoke 28 a, and a pair of combining portions 28 d eachconfigured to combine the fixture yoke 28 a and the opposite yoke 28 cwith each other. An opening 28 b is formed at the center of the pair ofopposite yokes 28 c and extends in the optical axis direction OA. Thehousing space 28 e is an internal space enclosed by the fixture yoke 28a, the opposite yokes 28 c, and the combining portions 28 d.

Since the fixture yoke 28 a and the opposite yokes 28 c are integrated,a closed magnetic path can be formed without increasing the number ofcomponents. The opposite yokes 28 c are located between the guide shaft23 and the coil 24, as illustrated in FIG. 4.

As illustrated in FIG. 4, the fixture portion 22 d that is locatedinside of the opening 28 b, the coil 24, and the magnet 29 are arrangedin the housing space 28 e of the yoke 28, and the coil 24 is locatedbetween the magnet 29 and the opposite yokes 28 c. The barrel unit canbe made smaller since the fixture portion 22 d, the coil 24, and themagnets 29 are located in the housing space 28 e.

Each magnet 29 has a plate shape, and a surface parallel to the opticalaxis direction OA. The magnets 29 include a pair of magnets 29 a and 29b, and are magnetized so that the front surface and the back surface canhave different polarities. As illustrated in FIG. 8, the magnets 29 aand 29 b are distant from each other by a predetermined interval (thisspace between them will be referred to as a “neutral zone NZ”), arrangedin the housing space 28 e of the yoke 28, and fixed onto the fixtureyoke 28 a of the yoke 28.

The magnet 29 a is located on the imaging plane side (or on the lowerside in FIG. 8), and contacts a projection 28 f formed on the fixtureyoke 28 a of the yoke 28. Thereby, the magnet 29 a is positioned. Themagnet 29 b is located on the object side (or on the upper side in FIG.8), and contacts a projection 28 g formed on the fixture yoke 28 a ofthe yoke 28. Thereby, the magnet 29 b is positioned.

FIGS. 9A to 9E are sectional views illustrating a movement of the coil24 relative to the magnets 29. In FIG. 9A, illustrates anon-image-pickup state and an image-pickup standby state of the lensholding frame 22, in which the coil 24 is located on the imaging planeside. FIG. 9B illustrates a state just before the driving forcegenerator of the coil 24 is transferred while the lens holding frame 22is moving. FIG. 9C illustrates a state in which the driving forcegenerator of the coil 24 is transferred while the lens holding frame 22is moving. FIG. 9D illustrates a state in which the driving forcegenerator of the coil 24 has been transferred while the lens holdingframe 22 is moving. FIG. 9E illustrates a maximum feeding state of thelens holding frame 22.

FIG. 10 is a partially sectional view of the barrel unit that is locatedat a non-image-pickup position. FIG. 11 is a partially sectional view ofthe barrel unit that is located at the image-pickup standby state. FIG.12 is a sectional view of the barrel unit when the lens holding frame 22is in the maximum feeding state and in the image pickup state.

The neutral zone NZ is set so that when the coil 24 is located at aposition illustrated in FIG. 9A the second driving force generator 24 cof the coil 24 does not generate a thrust parallel to the optical axisdirection OA. In addition, the neutral zone NZ is set so that when thecoil 24 is located at a position illustrated in FIG. 9E, the firstdriving force generator 24 b of the coil 24 does not generate a thrustparallel to the optical axis direction OA.

When the first driving force generator 24 b and the second driving forcegenerator 24 c are located in the neutral zone NZ, as illustrated inFIG. 9C, the current flows in the first driving force generator 24 b andthe second driving force generator 24 c in opposite directions. Sincetheir magnetic fields are also generated in opposite directions, thrustsare consequently generated in the same direction, which is parallel tothe optical axis direction OA.

The spring 30 is a compression spring that applies a biasing force tothe lens holding frame 22 in the feeding direction in thenon-image-pickup state. The guide shaft 23 is inserted into a hollowportion of the spring 30, and the guide shaft 23 is arranged between thefixture base plate 10 and the lens holding frame 22. One end of thespring 30 is supported on a top surface of the hollow cylinder portion10 c of the fixture base plate 10.

When the lens holding frame 22 is located at the non-image-pickupposition and the image-pickup standby position, as illustrated in FIGS.9A, 10, and 11, an overall region of the first driving force generator24 b opposes to the magnet 29 a and an overall region of the seconddriving force generator 24 c is located in the neutral zone NZ. Due tothe magnetic flux that passes a space between the opposite yoke 28 c andthe magnet 29 a, the first driving force generator 24 b generates athrust parallel to the optical axis direction OA. The lens holding frame22 is moved by this thrust in the optical axis direction OA.

In the middle of the movement of the lens holding frame 22, asillustrated in FIG. 9B, just before the second driving force generator24 c moves to a position opposite to the magnet 29 b, the overall regionof the first driving force generator 24 b is maintained opposite to themagnet 29 a. Therefore, similar to FIG. 9A, the first driving forcegenerator 24 b generates a thrust parallel to the optical axis directionOA, and the lens holding frame 22 is moved by this thrust in the opticalaxis direction OA.

As illustrated in FIG. 9C, when the first driving force generator 24 band the second driving force generator 24 c move in the neutral zone NZ,the first driving force generator 24 b opposes to the magnet 29 a andthe second driving force generator 24 c opposes to the magnet 29 b. Atthis position, the first driving force generator 24 b and the seconddriving force generator 24 c generate thrusts parallel to the opticalaxis direction OA due to the magnetic fluxes that pass the space betweenthe opposite yokes 28 c of the yoke 28 and the magnets 29 a and 29 b,and the lens holding frame 22 is moved by these thrusts in the opticalaxis direction OA.

As illustrated in FIG. 9D, when overall region of the second drivingforce generator 24 c opposes to the magnet 29 b, the overall region ofthe first driving force generator 24 b is located in the neutral zoneNZ. At this position, the second driving force generator 24 c generatesa thrust parallel to the optical axis direction OA due to the magneticfluxes that pass the space between the opposite yoke 28 c and the magnet29 b, and the lens holding frame 22 is moved by this thrusts in theoptical axis direction OA.

As illustrated in FIGS. 9E and 12, when the lens holding frame 22 islocated at a maximum feeding position, the overall region of the firstdriving force generator 24 b is located in the neutral zone NZ and theoverall region of the second driving force generator 24 c is located ata position opposite to the magnet 29 b. At this position, similar toFIG. 9D, the second driving force generator 24 c of the coil 24generates a thrust parallel to the optical axis direction OA, and thelens holding frame 22 is moved by this thrust in the optical axisdirection OA.

Second Embodiment

FIGS. 13A and 13B are sectional views illustrating a movement of thecoil 24 relative to the magnets 29 according to a second embodiment. InFIG. 13A, illustrates a non-image-pickup state and an image-pickupstandby state of the lens holding frame 22. FIG. 13E illustrates amaximum feeding state of the lens holding frame 22. A mechanicalstructure is similar to that of the first embodiment.

The second embodiment is different from the first embodiment in that inan entire movement range (driving stroke) of the lens holding frame 22,as illustrated in FIGS. 13A and 13E, an overall region of the drivingforce generator 24 b opposes to the magnet 29 a and an overall region ofthe driving force generator 24 c opposes to the magnet 29 b. Thisconfiguration can obtain a similar effect as that of the firstembodiment.

In the first and second embodiments, the coil 24 is fixed onto the lensholding frame 22 and the magnets 29 are fixed onto the yoke but the coil24 may be fixed onto the yoke and the magnet 29 may be fixed onto thelens holding frame 22.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

The driving unit is applicable to an application of driving an object.

This application claims the benefit of Japanese Patent Application No.2009-277314, filed Dec. 7, 2009, which is hereby incorporated byreference herein in its entirety.

1. A barrel unit comprising: a barrel; a holding member configured tohold an optical element; a coil fixed onto the holding member andarranged between a yoke and a magnet; a cylindrical member configured tosupport the barrel and the holding member; and a driving unit configuredto generate a thrust by electrifying the coil and to drive the holdingmember in an optical axis direction of the optical element by using thethrust, wherein the yoke, the magnet, and the coil are located outsideof a part of the cylindrical member which supports the barrel, whereinthe cylindrical member has a notch portion, wherein the holding memberincludes a body configured to hold the optical element, a sleeve portionconfigured to hold the coil, and an arm portion configured to connectthe sleeve portion to the body and to extend in a directionperpendicular to the optical axis direction, and wherein the arm portionpass the notch portion of the cylindrical member, and has a length suchthat the coil can be located outside of the part of the cylindricalmember.
 2. The barrel unit according to claim 1, wherein the yokeincludes a fixture yoke onto which the magnet is fixed, an opposite yokearranged parallel to the fixture yoke, and a combining portionconfigured to combine the fixture yoke and the opposite yoke with eachother, and wherein the coil and the magnet are arranged in an internalspace formed by the fixture yoke, the opposite yoke, and the combiningportion.
 3. The barrel unit according to claim 1, wherein the drivingunit further includes a guide shaft located outside of the part of thecylindrical member and configured to guide a movement of the holdingmember.
 4. The barrel unit according to claim 3, wherein the holdingmember includes a sleeve portion, the sleeve portion including anengagement portion engaged with the guide shaft, and a fixture portioninserted into an air core portion of the coil and configured to fix thecoil.
 5. The barrel unit according to claim 4, wherein a center axis ofthe guide shaft is orthogonal to a center axis direction of the coil. 6.The barrel unit according to claim 5, wherein the coil is symmetricallyarranged with respect to a plane that passes the center axis of theguide shaft and a center axis of the coil.
 7. The barrel unit accordingto claim 6, wherein the coil includes a winding portion in which thecurrent flows in a perpendicular direction to both the optical axisdirection and the center axis direction of the coil, and wherein an axisthat is parallel to the optical axis direction and halves a length ofthe winding portion in the perpendicular direction is located on theplane.
 8. An image pickup apparatus comprising a barrel unit, whereinthe barrel unit includes a barrel, a holding member configured to holdan optical element, a coil fixed onto the holding member and arrangedbetween a yoke and a magnet, a cylindrical member configured to supportthe barrel and the holding member, and a driving unit configured togenerate a thrust by electrifying the coil and to drive the holdingmember in an optical axis direction of the optical element by using thethrust, and wherein the yoke, the magnet, and the coil are locatedoutside of a part of the cylindrical member which supports the barrel,wherein the cylindrical member has a notch portion, wherein the holdingmember includes a body configured to hold the optical element, a sleeveportion configured to hold the coil, and an arm portion configured toconnect the sleeve portion to the body and to extend in a directionperpendicular to the optical axis direction, and wherein the arm portionpass the notch portion of the cylindrical member, and has a length suchthat the coil can be located outside of the part of the cylindricalmember.